(1) Field of the Invention
The field of this invention is that of devices for holding or storing water and more particularly that of the flow of rainwater and its regulation.
(2) Description of Related Art
A certain number of devices for holding rainwater, which have the purpose of a temporary storage or holding of water so as to regulate the flow that runs downstream from a given point in the case of a strong rain or overflow from a gutter, are known. Some of these devices are characterized by a cavity that is buried in the ground that makes it possible to produce a hydraulic buffer between a water intake, whose flow rate is suddenly very high, and a downstream pipe that can handle only a moderate flow rate. The water accumulates there during times of high flow and then evens out downstream through a calibrated drain. Other devices are designed such that the leak rate is set by natural infiltration rather than by a downstream pipe. These devices contribute to reconstituting the water tables when the geological conditions are favorable. Other devices also make it possible to hold the water that is accumulated partially or entirely for a subsequent use.
These devices are in general constituted by parallelepipedic tanks that are made of plastic, with perforated walls to allow the passage of water. They are assembled together so as to constitute a large block that can range from several tens to several thousands of m3, based on the size of the buffer that it is desired to produce. This buffer is placed inside the cavity, itself covered by one or more membranes that make(s) it possible to obtain—according to the type of membranes used—either a volume that is sealed with regard to the terrain in which it is laid and to conserve excess water over the time when it is evacuated via the calibrated drain, or else for a subsequent use, or a permeable volume from which the slow diffusion to the environment operates by infiltration.
Such devices are the object of patent applications such as, for example, the patents or patent applications FR2499515, EP0943737, EP1416099, EP1887145, JP63268823 or JP9112792. They are characterized by holding tanks, stacked two by two head to foot, which are parallelepiped in shape with one face open and the opposite face carrying columns that ensure the retaining structure of the upper tank layer.
So as to support significant weight, the central portion of these tanks is equipped with a large number of columns that, on the one hand, is detrimental to the amount of water that the tank can contain and, on the other hand, requires a large quantity of material to manufacture the tank. Since all of these tanks are manufactured by molding, their price, once the mold is amortized, is greatly dependent upon the quantity of material that constitutes it; the reduction of the volume of material therefore constitutes a competitive advantage that may prove decisive.